Described embodiments provide a rotor mounting boom assembly for a personal aircraft. The rotor mounting boom assembly includes a rotor mounting boom releasably attachable to a wing of the personal aircraft, one or more vertical lift rotors, and one or more rotor controller assemblies. controller assemblies for each rotor are positioned on the rotor mounting booms such that downwash from the rotor causes increased airflow across the controller assembly to cool the controller assembly components. A rotor controller enclosure includes an air inlet and an air outlet to allow airflow through the enclosure to cool the controller components. The air inlet is positioned relative to the path of the rotor blades such that the downwash from the rotor that flows into the air inlet is maximized. The structure of the enclosure includes features for increasing the airflow through the enclosure.
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1. A boom assembly for a personal aircraft, the boom assembly comprising:
a boom attachment interface to mount the boom assembly to a wing of the personal aircraft via;
a vertical lift rotor attachment interface to mount a vertical lift rotor to the boom assembly;
an air inlet positioned on the boom such that airflow generated by the vertical lift rotor is directed through the air inlet; and
a rotor controller enclosure internal to the boom assembly, the rotor controller enclosure comprising a location to install a rotor controller to control the vertical lift rotor, wherein the rotor controller enclosure is in fluid communication with the air inlet and an air outlet for allowing air to flow through the rotor controller enclosure.
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This application is a continuation of co-pending U.S. patent application Ser. No. 15/297,033, entitled VENTILATED ROTOR MOUNTING BOOM FOR PERSONAL AIRCRAFT filed Oct. 18, 2016 which is incorporated herein by reference for all purposes.
This disclosure relates generally to a rotor mounting boom for a personal aircraft configured to provide safe operations while achieving robust control and efficient maintenance. In particular, the described embodiments include a rotor mounting boom for an aircraft with vertical takeoff and landing capability. The rotor mounting boom includes a rotor and a controller assembly ventilated by rotor downwash.
Taking off and landing vertically, instead of using a runway to develop sufficient velocity on the ground for wings to provide adequate lift, requires an aircraft to provide both vertical and forward thrust. Thrust produced in the vertical direction provides lift to the vehicle; thrust produced horizontally provides forward movement. A vertical takeoff and landing (VTOL) aircraft can produce both vertical and horizontal thrust, and is able to control these forces in a balanced fashion.
The rotary wing aircraft, or helicopter, is one common type of VTOL aircraft. Helicopters have large rotors that provide both vertical and horizontal thrust. For the rotors to perform this dual function across a range of airspeeds, the rotors are typically quite complex. Depending on the vehicle flight condition, the rotor blades must be at different orientation angles around the 360 degrees of azimuth rotation to provide the needed thrust. Therefore, rotors have both collective and cyclic variation of the blade orientation angle. Collective varies the angle of each blade equally, independent of the 360-degree rotation azimuth angle. Cyclic varies the blade angle of attack as a function of the 360-degree rotation azimuth angle. Cyclic control allows the rotor to be tilted in various directions and therefore direct the thrust of the rotor forwards, backwards, left or right. This direction provides control forces to move the helicopter in the horizontal plane and respond to disturbances such as wind gusts.
Helicopter rotors are large and unprotected from hitting nearby obstacles. Additionally, they utilize mechanically complex systems to control both the collective and cyclic blade angles. Such rotors are mechanically complex and require maintenance. The rotors generally rotate at a low speed; this results in heavy transmissions between the rotor and motor. The transmissions, or gearboxes, decrease the vehicle payload potential, as well as vehicle safety. Because of the mechanical complexity across the entire vehicle system, many parts are single points of failure. Because of this lack of redundancy, frequent inspections and maintenance are required to keep the vehicle safe.
Other types of VTOL aircraft have multiple rotors to reduce the single points of failure. However, many vital components, such as motor controllers, are not duplicated, and are thus still single points of failure. These components are not duplicated due to design complexity, weight issues, and maintenance concerns. For example, a motor controller typically needs to be cooled, and including multiple conventional cooling systems on an aircraft increases design complexity and aircraft weight. Additionally, including multiple conventional cooling systems increases the chances that an aircraft will be taken out of service for maintenance.
Described embodiments provide a rotor mounting boom for a personal aircraft with a configuration that is safe and efficient as well as easy to maintain. In one embodiment, multiple rotor mounting booms are coupled to a wing of the personal aircraft and are removable and replaceable for maintenance. Each rotor mounting boom includes a forward rotor assembly and an aft rotor assembly, which enable the aircraft to accomplish vertical takeoff and landing with transition to and from forward flight. In one embodiment, each rotor mounting boom includes one or more rotor controller assemblies for controlling rotor operation by sending control signals to the rotors. The rotor mounting booms include an attachment interface for attachment to the wings of the personal aircraft. In one embodiment, the attachment interface allows the rotor mounting boom to be attached to the wing using releasable fasteners, such as screws or bolts, so that the rotor mounting boom may be easily removed from the wing for efficient repair or replacement.
In one embodiment, the aircraft configuration includes multiple rotors on multiple rotor mounting booms oriented to provide vertical thrust for lift and control during takeoff, transition to and from forward flight, and landing. The rotors are attached to the rotor mounting booms in fixed, non-planar orientations. The orientations of rotors provide lateral and, in some embodiments, fore and aft control of aircraft without requiring a change of attitude, and minimize disturbances to the flow when the aircraft is cruising. In various embodiments, the rotors have forward, backwards, left, and right orientations, and are located along the leading and trailing edge of the wing, with two or more rotors located on each side of the fuselage. Due to the multiple number and independence of the vertical lift rotors, the vertical thrust is redundant and thrust and control remain available even with the failure of any single rotor. Since there are multiple vertical rotors that provide large control forces, the rotors are smaller, with faster response rates for operation even in gusty wind conditions. In one embodiment, a separate electric motor and controller powers each vertical lift rotor, to provide lift system redundancy from failure of one or more lifting rotors.
Controller assemblies for each rotor are positioned on the rotor mounting booms such that downwash from the rotor causes increased airflow across the controller assembly, which allows for more effective cooling of controller assembly components and more efficient controller operation. In one embodiment, the controller assembly includes an enclosure that houses and protects controller components. The enclosure includes an air inlet and an air outlet to allow airflow through the enclosure to cool the controller components. In one embodiment, a heat exchanger such as a folded fin heat exchanger is included in the controller components to facilitate cooling of the other components using the air flowing through the enclosure. The air inlet is positioned relative to the path of the rotor blades such that the downwash from the rotor that flows into the air inlet is maximized. In one embodiment, the structure of the enclosure includes features for increasing the airflow through the enclosure. For example, the enclosure may include an inlet cowl and a nose cone to direct airflow through the enclosure. Additionally, the enclosure may include a raised portion aft of the air inlet that raises the air pressure around the air inlet to increase airflow into the air inlet.
In various embodiments, aircraft 100 is sized to accommodate a single pilot and personal cargo. For example, in various embodiments the length of the aircraft from nose to its aft-most surface is between 15 and 20 feet, and its wingspan is between 15 and 20 feet. In alternative embodiments, the aircraft may be longer or shorter, wider or narrower, as will be appreciated by those of skill in the art, without departing from the principles described here.
Aircraft 100 is constructed in various embodiments primarily of a composite material. Fuselage 107 and wing 104 are made from carbon fiber composite material. In alternative embodiments, the wing may have metal fittings and ribs attached to the inside and outside of a carbon fiber composite wing skin. In some embodiments the wing skin may comprise composite materials made of carbon fiber combined with other composite materials such as Kevlar. In other alternative embodiments, the fuselage may comprise a metal truss made from steel or aluminum with a composite skin that covers the truss. The composite fuselage skin in this embodiment may be made of carbon fiber, Kevlar, or other composite materials as understood by those of skill in the art. The cockpit windows in one embodiment are polycarbonate, though other lightweight clear plastics may also be used.
Rotor assemblies 101, 102 include rotors that in one embodiment have a 16 inch radius, and are made from carbon fiber composite material, and in an alternative embodiment from carbon fiber composite blades attached to an aluminum hub. In other embodiments, rotors are made from wood blades attached to an aluminum hub, or wood blades attached to a carbon fiber composite hub. The rotors may be a single piece that bolts onto the motor assembly. Rotor assemblies 101 are described further below.
Aircraft 100 includes a wing 104. The wing 104 has downward-angled wingtips 204 at its ends. The downward-angled wingtips provide lateral stability and decrease the drag due to lift on the wing. The particular wingtip shape is established for adequate stability, as will be understood by those skilled in the art.
Vertical lift rotor assemblies 101, 102 are mounted on each side of aircraft 100. In one embodiment, rotor mounting booms 114 (
Returning to
Rotor controller assemblies 506 include devices for controlling motor operation for rotor assemblies 101, 102, and may include a computer or other control system. As shown in
In one embodiment, the rotor controller assembly 506 includes an enclosure 510 that encases the components of the rotor controller assembly. In various embodiments, the rotor controller assemblies 506 include heat exchangers 570, such as a folded-fin heat exchanger to dissipate heat from the other components of the rotor controller assembly. The enclosure 510 may include one or more ventilation openings to allow air to more effectively circulate within the enclosure, allowing for increased performance of the heat exchanger 570. The enclosure 510 may further include airflow channels to direct air within the enclosure. In one embodiment, one or more air inlets 514 and one or more air outlets 516 are disposed on the enclosure 510 to facilitate airflow through the enclosure.
In one embodiment, the rotor controller assembly 506 is positioned on the rotor mounting boom 114 such that the downwash from the rotor causes increased airflow into an air inlet 514. For example, the rotor controller assembly 506 may be positioned below the rotor path 550, 552, as illustrated in
The vertical separation distance between the rotor path and each air inlet 514 is designed to maximize the downwash from the rotor that enters the air inlet 514. In one embodiment, the separation distance is approximately equal to the chord length of the rotor. In one embodiment, the separation distance is approximately equal to one half the chord length of the rotor. The position of the air inlet 514 along the radius of the rotor path 550, 552 is also designed to maximize the downwash from the rotor that enters the air inlet 514. Rotor downwash intensity as a function of the radius of the rotor path is roughly proportional to lift as a function of the radius. The maximum lift is achieved at a distance of two-thirds of the radius from the center of the rotor, so the maximum downwash is present at this location as well. Accordingly, in one embodiment, the air inlet 514 is located below the outer 50% of the rotor path radius so that the part of the rotor generating the most downwash is directly above the air inlet.
The structure of the enclosure 510 may further increase airflow through the enclosure and thus heat exchanger efficiency. Turning to
The rotor mounting boom of
In various embodiments, the arrangement of the components described with respect to
The rotor mounting boom of
The rotor mounting boom of
The rotor mounting boom of
The rotor mounting boom of
As noted, aircraft 100 includes multiple rotor mounting booms 114 and rotor assemblies 101, 102 per side. The vertical lift rotors generate thrust that is independent of the thrust generated by the forward flight propellers 103 during horizontal cruise. The vertical lift rotors provide enough thrust to lift the aircraft off the ground and maintain control. In one embodiment, each rotor generates more, e.g., 40% more, thrust than is needed to hover, to maintain control in all portions of the flight envelope. The rotors are optimized by selecting the diameter, blade chord, and blade incidence distributions to provide the needed thrust with minimum consumed power at hover and low speed flight conditions. In various embodiments, half of the rotors rotate in one direction, and the other half rotate in the opposite direction to balance the reaction torque on the aircraft. In some embodiments, rotors mounted on the same rotor mounting boom have opposite directions of rotation. In other embodiments rotors mounted on the same rotor mounting boom have the same direction of rotation. In some embodiments, the rotors may be individually tuned to account for different interactions between the rotors, or between the airframe and the rotors. In such embodiments the tuning includes adjusting the incidence or chord distributions on the blades to account for favorable or adverse interactions and achieve the necessary performance from the rotor. In the embodiment illustrated in
In one embodiment, the forward vertical lift rotor assemblies 101 located in front of the CG and the aft vertical lift rotor assemblies are located behind the CG. In this manner, the center of lift of the rotors in hover is co-located with the center of gravity of the aircraft 100. This arrangement permits a variation of longitudinal or lateral positioning of the payload in the fuselage 107. A flight computer modifies the thrust produced by each vertical lift rotor independently, providing a balanced vertical lift or, alternatively, unbalanced lift to provide control.
In some embodiments, the rotor orientation provides lateral and longitudinal control of the aircraft without requiring a change of attitude. Because rotor assemblies 101, 102 are each mounted to cant outward, inward, forward, or back, a proper combination of rotor thrusts results in a net force in the horizontal plane, as well as the needed vertical lift force. This is helpful when maneuvering near the ground, for example. In addition, in the case of a rotor failure in which a blade becomes damaged or separated, the different cant angles make it less likely that another rotor will be damaged, thus making the design more failure tolerant. The orientations are also chosen to minimize disturbances to the flow when the aircraft is cruising. In some embodiments, the orientation of the rotors is varied forward, backward, left, and right, enabling the aircraft to maneuver in any direction without changing attitude. In other embodiments, the orientation is varied only left and right, minimizing the disturbance to the flow during cruise, but meaning that the aircraft can only maneuver side-to-side, not forward and backward, without changing attitude.
Forward flight propellers 103 provide the thrust for transition to forward flight, climb, descent, and cruise. In one embodiment two or more forward thrust propellers 103 are mounted along the span of the horizontal stabilizer 105. In alternative embodiments, a single forward thrust propeller is mounted on the aft portion of the fuselage 107 at the center of the span. In other embodiments, one or more propellers are mounted to the front of the wing 104 or propulsion booms as tractor propellers. The propellers can be rotated in opposite directions so that the torque required to turn them does not produce a net torque on the airplane. Also, the thrust of the two propellers can be varied differentially to provide a yaw control moment. Positioning on the wing results in less inflow disturbance to the propellers. Use of a single propeller on the fuselage permits fewer components and less weight, but with a different-sized motor and with the inflow including disturbances from the fuselage. In one embodiment, the forward propellers are fixed-pitch. The chord and incidence distributions are optimized to provide adequate thrust for acceleration and climbing both when the vehicle is moving slowly and supported in the air by the thrust of the rotors and when the aircraft is moving quickly and is fully supported by the lift of the wings. Additionally, the chord and incidence distributions are selected to provide efficient thrust at the cruising speed of the aircraft. In other embodiments the forward propellers utilize a variable pitch mechanism which allows the incidence of each blade to be adjusted depending on the flight condition.
The vertical lift rotors and the forward propellers may be driven by electric motors that are powered by a power system. In one embodiment the power system includes a battery that is attached to one motor controller for each motor. In one embodiment the battery comprises one or more modules located within the fuselage of the aircraft. In other embodiments the battery modules are located in the propulsion booms. The battery provides a DC voltage and current that the motor controllers turn into the AC signals that make the motors spin. In some embodiments the battery comprises lithium polymer cells connected together in parallel and in series to generate the needed voltage and current. Alternatively, cells of other chemistry may be used. In one embodiment the cells are connected into 93 cell series strings, and 6 of these strings are connected in parallel. In other embodiments, the cells are connected with more or fewer cells in series and more or fewer cells in parallel. In alternative embodiments, the rotors and propellers are powered by a power system that includes a hybrid-electric system with a small hydrocarbon-based fuel engine and a smaller battery. The hydrocarbon engine provides extended range in forward flight and can recharge the battery system.
As noted, the use of multiple independently controlled rotors provides a redundant lift system. For example, a system that includes six or more rotors permits hover and vertical ascent/descent with safe operation without forward airspeed, even if one or several individual components fail.
Landing gear is provided with wheels to permit the aircraft to move while on the ground. The landing gear may retract into the fuselage 107 while the aircraft is in flight. In other embodiments the landing gear is a skid and has no wheels, since the aircraft is capable of takeoff and landing without forward movement. In some embodiments, some or all of the wheels are fitted with electric motors that allow the wheels to be driven. Such motors allow the vehicle to be self-propelled while on the ground.
In addition to the embodiments specifically described above, those of skill in the art will appreciate that the invention may additionally be practiced in other embodiments. For example, in an alternative embodiment, aircraft 100 is designed to accommodate two or more occupants. In such an embodiment, the wingspan is larger, the rotors have a larger diameter, and the fuselage 107 is wider. In an alternative embodiment, aircraft 100 is an unmanned vehicle that is capable of flight without a pilot or passengers. Embodiments without passengers have additional control systems that provide directional control inputs in place of a pilot, either through a ground link or through a predetermined flight path trajectory.
Although this description has been provided in the context of specific embodiments, those of skill in the art will appreciate that many alternative embodiments may be inferred from the teaching provided. Furthermore, within this written description, the particular naming of the components, capitalization of terms, the attributes, data structures, or any other structural or programming aspect is not mandatory or significant unless otherwise noted, and the mechanisms that implement the described invention or its features may have different names, formats, or protocols. Further, some aspects of the system including components of the flight computer 700 may be implemented via a combination of hardware and software or entirely in hardware elements. Also, the particular division of functionality between the various system components described here is not mandatory; functions performed by a single module or system component may instead be performed by multiple components, and functions performed by multiple components may instead be performed by a single component. Likewise, the order in which method steps are performed is not mandatory unless otherwise noted or logically required.
Unless otherwise indicated, discussions utilizing terms such as “selecting” or “computing” or “determining” or the like refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system memories or registers or other such information storage, transmission or display devices.
Electronic components of the described embodiments may be specially constructed for the required purposes, or may comprise one or more general-purpose computers selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer readable storage medium, such as, but is not limited to, any type of disk including floppy disks, optical disks, DVDs, CD-ROMs, magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, application specific integrated circuits (ASICs), or any type of media suitable for storing electronic instructions, and each coupled to a computer system bus.
Finally, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter. Accordingly, the disclosure is intended to be illustrative, but not limiting, of the scope of the invention.
Long, Geoffrey Alan, Tighe, James Joseph, Tzarnotzky, Uri
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